BjornF16 Wrote:Doh!...didn't do my homework. All my lowers are RRA or AA; I was reminded today that the Colt upper has the "large" diameter hole for their front pivot. Someone suggested some bushings...anyone using bushings on Colt upper/mil spec lower?Negative, no problem. A Colt 6933 upper has mil-spec take down pin dimensions. The large hole stuff is only an issue with early commercial stuff. Newer Colt uppers and lowers are standard dimension, and the newest Colt lowers even went back to standard size hammer and trigger pins. The only thing left in their new receivers is the web they leave unmilled to preclude the use of a drop in auto sear.
ETA some pics:
Mine....
![[Image: 5a749924.jpg]](http://i307.photobucket.com/albums/nn291/Variable556/5a749924.jpg)
Colt "H" buffer....
![[Image: ec051c5b.jpg]](http://i307.photobucket.com/albums/nn291/Variable556/ec051c5b.jpg)
Standard sized takedown pins....
![[Image: 30079182.jpg]](http://i307.photobucket.com/albums/nn291/Variable556/30079182.jpg)